I thought the JFK controller was very restrained.... He did not start shouting over the radio like they usually do.
The tower controller is a poorly trained idiot. Any casual observer can guess that heavier aircraft take longer to stop. If the tower controller had requested the 787 before landing that he needed him to vacate U3 they he might have been able to modify his autobrake/reverse plan but telling him on the rollout has zero chance of success. Additionally, none of the exits qualify as a high-speed taxiway. Both U3 and V3 require slowing to walking pace before vacating as the 90deg turn will happily rip the tyres off the rims if you try and do it faster. Putting a heavy aircraft 4 miles behind another heavy on a runway with an LDA of only 2570m/8436' has a pretty fair chance of failure...... But you can't tell them that.... they think they know it all.